Wireless endpoint dhcp issue

[lazuardinurfaiz15]

Hi all.

I am using WLC 3504 and AP air-ap3802I-F-K9 with firmware 8.5.151.0 configured as flexconnect AP. We have 3 SSIDs, 2 of them are using dot1x and the rest is PSK.

Once a day, there is a random client (not happen to all client) having difficulties to get an ip address from DHCP server. This issue happen on all SSID. I would have to issue ipconfig /renew on the endpoint, after that the client will get an ip address from DHCP server.

Please help me to troubleshoot this case, thank you.

[Sandeep Choudhary]

Hi,

does this happen on both bands (2.4GHz and 5GHz) ?

one thing to check on your switches if ip helper address is pointing to your DHCP server or IP helper configured on vlan !

Can you chekc if there are specifc clients are having issues or all types clients ?

Regards

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[lazuardinurfaiz15]

Hi Sandeep.
- does this happen on both bands (2.4GHz and 5GHz) ?
Yes it does.
- check on your switches if ip helper address is pointing to your DHCP server or IP helper configured on vlan
There is ip helpder addresss on the correspondance interface vlan. Since not all the endpoint on that vlan is having that issue. Only small number of client and this issue is not happen all the time.
- Can you chekc if there are specifc clients are having issues or all types clients ?
I have not able to identify about the spesific client since almost all type of client is having this issue (notebook/smartphone, windows10/windows7, lenovo/hp), but this issue is mostly happen on the notebook running windows 7 in hp brand.

Thank you

[Jay Vivas]

Before you do the release/renew have you checked the regular ipconfig? Is there a current address assigned to the client in a different subnet? Since a release/renew fixes the issue I am assuming the AP and SSID they are currently using are configured correctly. Something we commonly see is that a client(mostly with Windows) might connect to an SSID and pull an ip address from subnet1. Then, this client might go to a different site where they use subnet 2 for the same SSID. Since the client already has a valid lease it wont do dhcp again and therefore gets stuck using a ip address from subnet 1 while connected to a vlan tied to subnet 2. It is possible, if you are using local switching, that one AP is not configured correctly(flex group or ap specific vlan mapping) and when clients start on that AP and move to another we see the same problem. I would check what ip address the client has before you fix the problem.

[Scott Fella]

So you guys’ve FlexConnect enabled, can you verify that all the wlans are mapped to the correct corresponding vlan and that all the AP’s are connected to a trunk port? Make sure fast ssid is enabled especially if you have more than one ssid and users might switch to different ones or if devices automatically switch to a different ssid.